Sprinkler system kept blowing the fuse

The winter raining season is almost over. It’s time to turn on the sprinkler system to keep the lawn green. When I did that over a week ago, I noticed that the sprinklers did not work. I went to check on the automatic sprinkler system and noticed that the power was off; the backup battery was keeping the system up with a display of “POWEROFF.” I traced the problem being the fuse was blown. No problem. I went to Fry’s and bought a box of 5 fuses (Glass type: 3AG 500mA) at 750mA (Fry’s ran out of the 500mA type). So I replaced the fuse. Done.

After a couple of days, I noticed the sprinkler still did not turn on. (I should have checked the sprinkler in manual mode – a lesson to be learned – validate your fix immediately.) I then spent sometime to manually stepping through each station and found that the fuse gets blown during station 1. So I removed the wire to station 1 and verified that the wire has been shorted. I suspected that the transformer for Station 1 may be broken/shorted.

During the weekend, I checked the entire wiring for all the wires and found that the wires were all cracked up under the sun. After some debugging, the short (1~2 ohm vs. 25 ohm normally) turns out to be at the mid point at the exit point of the house, not at/near the sprinkler station. I took the opportunity to replace all of the wire joints and added brand new insulating electrical tape to the wiring. The problem was then fixed.